SYSTEMS AND METHODS TO SYNCHRONIZE WIRELESS DEVICES IN THE PRESENCE OF A FMCW RADIO ALTIMETER

• US 20170180072A1
• Filed: 12/17/2015
• Published: 06/22/2017
• Est. Priority Date: 12/17/2015
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Timm, Steven L., Franceschini, Michael R., Muldoon, Kelly P.
• Granted Patent: US 10,177,868 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: H04B 7/18502 Airborne stations
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/046 the resource being in the space domain, e.g. beams

Abstract

Systems and methods to synchronize wireless device nodes in the presence of a FMCW radio altimeter are provided. In one embodiment, a wireless device network comprises: a plurality of device nodes that share a radio frequency spectrum using time-division multiple accesses; a network synchronizing device in wireless communication with the plurality of device nodes, the network synchronizing device coupled to a timeslot allocation function, wherein the timeslot allocation function allocates to the network synchronizing device a timeslot on a first designated synchronization channel within the radio frequency spectrum; wherein the network synchronizing device broadcasts an arbitrary timeslot synchronization beacon to the plurality of device nodes on the first designated synchronization channel in the timeslot; wherein the arbitrary timeslot synchronization beacon comprises a Sync Timeslot identifier that identifies the timeslot, and a Sync Time indicator that includes a time that the arbitrary timeslot synchronization beacon was transmitted.

Claims

1. A wireless device network, the network comprising:

a plurality of device nodes that share a radio frequency spectrum using time-division multiple accesses;

a network synchronizing device in wireless communication with the plurality of device nodes, the network synchronizing device coupled to a timeslot allocation function, wherein the timeslot allocation function allocates to the network synchronizing device a timeslot on a first designated synchronization channel within the radio frequency spectrum;

wherein the network synchronizing device broadcasts an arbitrary timeslot synchronization beacon to the plurality of device nodes on the first designated synchronization channel in the timeslot;

wherein the arbitrary timeslot synchronization beacon comprises a Sync Timeslot identifier that identifies the timeslot, and a Sync Time indicator that includes a time that the arbitrary timeslot synchronization beacon was transmitted.

2. The network of claim 1, wherein the plurality of device nodes each comprise a Timeslot Counter, a Slot Time Clock, and a processor;

wherein the processor is configured to update the Timeslot Counter based on the Sync Timeslot and update the Slot Time Clock based on an offset correction calculated as a function of the Sync Time and a Correction Factor.

3. The network of claim 2, the plurality of device nodes each further comprising a memory, wherein the Correction Factor is a constant stored in the memory.

4. The network of claim 2, wherein the Correction Factor is a time delay value estimate of a one way delay starting from a moment the Sync Time is inserted into the arbitrary timeslot synchronization beacon until is it extracted at a receiving device node.

5. The network of claim 1, further comprising:

a radio altimeter tracking filter, wherein the radio altimeter tracking filter monitors and characterizes a radio altimeter signal transmitted by a frequency-modulated continuous wave radio altimeter, wherein the frequency-modulated continuous wave radio altimeter transmits the radio altimeter signal across the radio frequency spectrum that includes the first designated synchronization channel;

wherein based on data provided by the radio altimeter tracking filter, the timeslot allocation function predictively identifies timeslots in the first designated synchronization channel that will not conflict with the radio altimeter signal.

6. The network of claim 5, wherein the timeslot allocation function is integrated with one or both of the radio altimeter tracking filter or the network synchronizing device.

7. The network of claim 1, wherein the plurality of device nodes comprise a plurality of wireless avionics devices.

8. The network of claim 1, wherein the arbitrary timeslot synchronization beacon is transmitted at a start of the timeslot.

9. The network of claim 1, wherein the plurality of device nodes comprise at least a first subnet of device nodes and a second subnet of device nodes;

wherein the network synchronizing device transmits a first arbitrary timeslot synchronization beacon on the first designated synchronization channel utilized by the first subnet of device nodes; and

wherein the network synchronizing device transmits a second arbitrary timeslot synchronization beacon on a second designated synchronization channel utilized by the second subnet of device nodes.

10. A network synchronizing device for a wireless system network, the device comprising:

a wireless radio interface; and

a processor coupled to a memory;

wherein based on a clock signal from a Master Wireless Clock, the processor maintains a Master Timeslot Counter that indicates a current timeslot of a current wireless system frame, and a Master Slot Time Clock that defines starting and ending edges of the current timeslot;

wherein the processor is configured to receive a timeslot allocation from a Wireless Timeslot Allocation Function that indicates a timeslot in which it is permitted to transmit an arbitrary timeslot synchronization beacon on a first designated synchronization channel;

wherein when the timeslot occurs, the processor transmits, via the wireless radio interface, the arbitrary timeslot synchronization beacon, the arbitrary timeslot synchronization beacon comprising a Sync Timeslot identifier as indicated by the Master Timeslot Counter and a Sync Time indicator that indicates a time that the arbitrary timeslot synchronization beacon was transmitted.

11. The device of claim 10, wherein the Sync Time indicator is derived from a time value provided by the Master Slot Time Clock, the Master Wireless Clock, or both.

12. A method for synchronizing a wireless network sharing a radio spectrum with a radio altimeter, the method comprising:

receiving a time divisional multiple access (TDMA) timeslot allocation for a first frequency channel, wherein the first frequency channel comprises a frequency spectrum periodically shared with a radio altimeter signal; and

transmitting an arbitrary timing synchronization beacon (ATSB) during a timeslot indicated by the timeslot allocation, wherein the arbitrary timing synchronization beacon includes a sync timeslot identifier that indicates the timeslot in which the arbitrary timing synchronization beacon was transmitted and a sync time indicator identifying a time the arbitrary timing synchronization beacon is transmitted.

13. The method of claim 12, further comprising:

synchronizing a timeslot timing at a device node with a wireless network based on the arbitrary timing synchronization beacon.

14. The method of claim 13, wherein synchronizing a timeslot timing at the device node comprises:

updating a Timeslot Counter at the device node based on the Sync Timeslot identifier;

updating a Slot Time Clock at the device node based on an offset correction calculated as a function of the sync time indicator and a correction factor.

15. The method of claim 13, further comprising retrieving the correction factor from a memory at the device node.

16. The method of claim 15, wherein the Correction Factor is a time delay value estimate of a one way delay starting from a moment the Sync Time indicator is inserted into the arbitrary timeslot synchronization beacon until is it extracted at a receiving device node.

17. The method of claim 12, wherein transmitting the arbitrary timing synchronization beacon (ATSB) further comprises wirelessly broadcasting the arbitrary timing synchronization beacon to a plurality of wireless avionics devices aboard an aircraft.

18. The method of claim 12, further comprising:

characterizing the radio altimeter signal to predictively identify timeslots in the first frequency channel that will not conflict with the radio altimeter signal.

19. The method of claim 12, further comprising:

receiving the time divisional multiple access (TDMA) timeslot allocation from a timeslot allocation function, wherein the timeslot allocation function receives inputs from a radio altimeter tracking filter that indicates a current amplitude and period of the radio altimeter signal;

wherein timeslot allocation function allocates the timeslot for the first frequency channel based on the inputs from the radio altimeter tracking filter.

20. The method of claim 12, further comprising:

transmitting a first arbitrary timeslot synchronization beacon on a first designated synchronization channel utilized by a first subnet of device nodes; and

transmitting a second arbitrary timeslot synchronization beacon on a second designated synchronization channel utilized by a second subnet of device nodes.